Resorcinol formaldehyde latex (RFL) compositions have been used to treat textile substrates to enhance the substrates' adhesion to rubber-containing materials for textile reinforced rubber products such as tires, conveyor belts, transmission belts, and other composite materials. The presence of formaldehyde in traditional RFL compositions can present multiple health hazards. For example, since formaldehyde is very volatile (e.g. it is a gas at room temperature), it may be undesirably emitted during the process of use, which, without proper ventilation, could be a potential health risk in inhaled. Also, formaldehyde may be lost in a convection oven during drying at elevated temperature. Therefore, the efficiency of a process that utilizes formaldehyde may not be optimized due to this raw material loss.
Another problem associated with the use of traditional RFL compositions is that textile materials that have been treated with these RFL compositions typically lose their flexibility and are very stiff. Some end-use applications require a certain amount of flexibility in the RFL-treated article in order for the treated article to be use-able. Typical RFL compositions struggle to meet these flexibility requirements.
Furthermore, due to their relatively high reactivity levels, many RFL compositions are unstable at room temperature. Certain lattices cannot be made commercial due to the short shelf life of typical RFL compositions.
Finally, improving the adhesion strength between a textile material and a rubber compound is also desirable for optimized robustness and durability of the resulting textile-rubber composite. In this regard, traditional RFL compositions can still be improved to provide even greater adhesion between textile substrates and rubber. In one aspect, this feature is exemplified in automobile tires wherein the adhesion of fabric to tire rubber is an important safety feature which aids in preventing the tire from deteriorating during use.
Thus, one embodiment of this invention provides a composition comprising 2-furfuraldehyde and/or a reaction product of 2-furfuraldehyde to provide improved adhesion without the problems mentioned above. The 2-furfuraldehyde component has a boiling point of 160° C. (vs. −19° C. of formaldehyde, a gas at room temperature) and is much less likely to volatilize in a drying oven than formaldehyde. The 2-furfuraldehyde component also exhibits a significantly lower toxicity profile than formaldehyde. A textile material treated with the composition of this invention is much softer and more flexible than a traditional RFL-treated textile, and the resulting textile-rubber composite material is also much softer and more flexible. The 2-furfuraldehyde containing composition is also more stable than a formaldehyde-containing composition. Adhesion of materials to various rubbers and textile materials is improved using the composition of the present invention.